Cylinder blade for a mower

ABSTRACT

A cylinder cutting blade for a lawn mower characterized in that it comprises at least two modular cylinder cutting blade sections each modular cylinder cutting blade section effectively being a short cylinder cutting blade which are rotationally connected together in succession in such a manner that rotation of one modular cylinder cutting blade section results in rotation of the other modular cylinder cutting blade section to form the cylinder cutting blade. The cylinder cutting blade comprising: a longitudinal axis; a plurality of cutting bars which spiral around the longitudinal axis; a frame to hold the cutting bars in their respective positions characterized in that the cylinder cutting blade is constructed from at least two modular cylinder cutting blade sections, each modular cylinder cutting blade section comprising: a longitudinal axis; a plurality of cutting bars which spiral around the longitudinal axis; a frame to hold the cutting bars in their respective positions; and a locking mechanism; herein the modular cylinder cutting blade sections are mounted in succession so that their axes are substantially co-axial and the locking mechanism of each modular cylinder cutting blade section interacts with the locking mechanism of adjacent modular cylinder cutting blade sections to rotatably lock the modular cylinder cutting blade section to the adjacent modular cylinder cutting blade sections so that rotation of the modular cylinder cutting blade section results in rotation of adjacent modular cylinder cutting blade sections.

[0001] The present invention relates to lawn mowers and in particular to cylinder cutting blades for lawn mowers.

[0002] The use of cylinder cutting blades is well known in the art of lawn mowers. Cylinder cutting blades comprise a plurality of cutting bars mounted on a frame which spiral around, in a helical fashion, the longitudinal axis of the cylinder cutting blade. The radial distance of the outer edge of the cutting bars from the longitudinal axis remains constant along the length of the cutting bars.

[0003] The cylinder cutting blade is mounted in the front of a lawn mower and rotated by a motor about its longitudinal axis. A stationary shear blade is located in close proximity to the path swept out by the outer edge of the rotating cutting bars so that any vegetation such as grass is sheared by the action of the rotating cutting bars shearing the vegetation against the shear blade. The helical design of the cutting bars ensure that a smooth shearing action takes place.

[0004] Traditional designs of cylinder cutting blade have metal cutting bars which are welded onto a metal frame. This results in a structure which is complicated and expensive to make.

[0005] GB 2,116,413 discloses a cylinder cutting blade which comprises a blade holder upon which are mounted disposable plastic blades. Such a construction, however, is complicated.

[0006] According to the first aspect of the present invention, there is provided a cylinder cutting blade for a lawn mower characterised in that it comprises at least two modular cylinder cutting blade sections which are rotationally connected together in succession in such a manner that rotation of one modular cylinder cutting blade section results in rotation of the other modular cylinder cutting blade section.

[0007] By manufacturing, the cylinder cutting blade in this manner, it provides a simple and cheap construction. Furthermore, it allows cutting cylinders of different lengths to be manufactured from one design of modular cylinder cutting blade section. The length of the blade is increased by increasing the number of modular cylinder cutting blade sections used.

[0008] It will be appreciated by a person skilled in the art that this invention can be utilised with any design of cylinder blade for a lawn mower. Each modular cylinder cutting blade section is effectively a short cylinder cutting blade which can be connected in series to an adjacent one to make a longer cutting blade.

[0009] The cylinder cutting blade can be constructed from at least two modular cylinder cutting blade sections, each modular cylinder cutting blade section having a longitudinal axis and a locking mechanism wherein the modular cylinder cutting blade sections are mounted in succession so that their axes are substantially co-axial and the locking mechanism of each modular cylinder cutting blade section interacts with the locking mechanism of adjacent modular cylinder cutting blade sections to rotationally lock that modular cylinder cutting blade section to the adjacent modular cylinder cutting blade sections so that rotation of one modular cylinder cutting blade section results in rotation of the adjacent modular cylinder cutting blade sections.

[0010] The cylinder cutting blade preferably comprises:

[0011] a longitudinal axis;

[0012] a plurality of cutting bars which spiral around the longitudinal axis;

[0013] a frame to hold the cutting bars in their respective positions characterised in that the cylinder cutting blade is constructed from at least two modular cylinder cutting blade sections, each modular cylinder cutting blade section comprising:

[0014] a longitudinal axis;

[0015] a plurality of cutting bars which spiral around the longitudinal axis;

[0016] a frame to hold the cutting bars in their respective positions; and

[0017] a locking mechanism;

[0018] wherein the modular cylinder cutting blade sections are mounted in succession so that their axes are substantially co-axial and the locking mechanism of each modular cylinder cutting blade section interacts with the locking mechanism of adjacent modular cylinder cutting blade sections to rotatably lock the modular cylinder cutting blade section to the adjacent modular cylinder cutting blade sections so that rotation of the modular cylinder cutting blade section results in rotation of adjacent modular cylinder cutting blade sections.

[0019] According to the second aspect of the present invention, there is provided a lawn mower having a cylinder cutting blade characterised in that it comprises at least two modular cylinder cutting blade sections which are rotationally connected together in succession in such a manner that rotation of one modular cylinder cutting blade section results in rotation of the other modular cylinder cutting blade section to form the cylinder cutting blade.

[0020] According to the third aspect of the present invention, there is provided a modular cylinder cutting blade section characterised in that it is capable of connecting to at least one other modular cylinder cutting blade section in succession to form a longitudinal cylinder cutting blade so that rotation of the modular cylinder cutting blade section results in rotation of the other modular cylinder cutting blade section.

[0021] The invention will now be described with reference to the accompanying drawings, of which:

[0022]FIG. 1 shows a perspective view of a cylinder cutting blade;

[0023]FIG. 2 shows a perspective view of a first end of a modular cylinder cutting blade section of the cylinder cutting blade;

[0024]FIG. 3 shows a first end of the modular cylinder cutting blade section of the cylinder cutting blade;

[0025]FIG. 4 shows a second end of the modular cylinder cutting blade section of the cylinder;

[0026]FIG. 5 shows a side view of the modular cylinder cutting blade section;

[0027]FIG. 6 shows a second side view of the modular cylinder cutting blade section with the modular section rotated about its longitudinal axis relative to FIG. 5; and

[0028]FIG. 7 shows a perspective view of one end of the cylinder blade.

[0029]FIG. 1 shows an example of a fully assembled cylinder cutting blade according to the present invention. The cylinder cutting blade comprises five cutting bars (generally indicated as 2 in FIG. 1) which spiral around a central tubular core (4). The rate at which and the direction in which the cutting bars (2) spiral around the central tubular core (4) is constant. The outer edges (6) of the cutting bars (2) are located at a constant radial distance from a longitudinal axis (8) of the central tubular core (4), the longitudinal axis (8) of the central tubular core (4) also being the longitudinal axis of the cylinder cutting blade.

[0030] The cylinder cutting blade is constructed from six modular cylinder cutting blade sections (10; 12; 14; 16; 18; 20) (as shown in FIG. 1) which are mounted together in succession on a steel tube (not shown) which passes through the tubular core (4) of each of the modular cylinder cutting blade sections (10; 12; 14; 16; 18; 20) to form the cylinder cutting blade. Each modular cylinder cutting blade section (10; 12; 14; 16; 18; 20) is effectively a short cylinder cutting blade which, when mounted in succession on the steel tubes, form the longer cylinder cutting blade.

[0031] Each of the six modular cylinder cutting blade sections (10; 12; 14; 16; 18; 20) are identical in shape to the other five modular cylinder cutting blade sections (10; 12; 14; 16; 18; 20).

[0032] A modular cylinder cutting blade section (10; 12; 14; 16; 18; 20) shall now be described with reference to FIGS. 2 to 6.

[0033] Each modular cylinder cutting blade section (10; 12; 14; 16; 18; 20) comprises a central tubular core (4) having a longitudinal axis (8), the longitudinal axis (8) of the central tubular core (4) also being the longitudinal axis of the modular cylinder cutting blade section (10; 12; 14; 16; 18; 20).

[0034] Extending radially outwards from a first end (22) (shown facing in FIG. 4) of the central tubular core (4) are five support arms (24). Extending radially outwards from a second end (26) (shown facing in FIG. 3) of the central tubular core (4) are five more support arms (28). The five support arms (24) located around the first end (22) are angularly spaced around the longitudinal axis (8) by equal amounts so that there is an angle of 72° between adjacent support arms (24). Similarly, the five support arms (28) located around the second end (26) are angularly spaced around the longitudinal axis (8) by equal amounts so that there is an angle of 72° between adjacent support arms (28). However, the angular positions of the support arms (28) which extend from the second end (26) are twisted by 36° around the longitudinal axis (5) in relation to the support arms (24) which extend from the first end (22) so that they lie angularly midway between the support arms (24) extending from the first end (22).

[0035] Attached to ends of the support arms (24; 28) are the cutting bars (2). Each cutting bar (2) extends perpendicularly from the end of a support arm (24) which extends from the first end (22) to the end of a support arm (28) which extends the second end (26). The cutting bars (2) are curved and spiral around the longitudinal axis (8) of the central tubular core (4) at uniform rate through 36° in a helical manner. The outer edges (6) of the cutting bars (2) are radially equidistant from the longitudinal axis (8).

[0036] A flange (30) extends sideways from each of the front of the support arms (24) extending from the first end (22) in a direction tangential to the longitudinal axis (8). Similarly, a flange (32) extends sideways from each of the rear of the support arms (28) extending from the second end (26) in a direction tangential to the longitudinal axis (8) but in the opposite direction around the longitudinal axis (8) to that of the flanges (30) on the front support arms (24).

[0037] Formed at the first end (22) of the central tubular core (4) are rectangular castellations (34) which project from the first end (22) in a direction perpendicular to that of the longitudinal axis (8).

[0038] Formed in the second end (26) of the central tubular core (4) are rectangular recesses (36). The dimensions of the rectangular recesses correspond to those of the castellations (34) so that the castellations (34) of one modular cutting cylinder section (10; 12; 14; 16; 18; 20) are able to slot into the recess of another modular cutting cylinder section to form a tight fit.

[0039] Each modular cylinder cutting blade section is formed from glass filled polyamide (glass filled nylon) in a one piece construction.

[0040] Each modular cutting blade section (10; 12; 14; 16; 18; 20) is moulded using a two piece mould. In order for a two piece mould to be used, the length D has to be less than a predetermined amount due to the curvature of the spirallying cutting bars (2).

[0041] The maximum length D (as best seen in FIG. 5) is $\frac{{\Pi \left( {S + {2t}} \right)} - {2{nc}}}{n\left( {{\tan \quad \theta_{1}} + {\tan \quad \theta_{2}}} \right)}$

[0042] where S is the diameter of the internal bore 100 of the tubular core (4);

[0043] c is the size of the tooling land (see FIG. 7);

[0044] t is the thickness of the tubular core (4);

[0045] θ₁ is the helix angle at the outer diameter of the tubular core (4);

[0046] θ₂ is is the shut off angle; and

[0047] n is the number of cutting bars.

[0048] In this particular embodiment, S=25, t=2.5, θ₂=4.15, θ₁=6.8, c=4.5, and n=5.

[0049] The cylinder cutting blade is assembled as follows.

[0050] A first modular cylinder cutting blade section (10) is mounted onto a steel tube (not shown) by passing the steel tube through its central tubular core (4). The diameter of the steel tube is slightly less than that of the diameter of the bore (38) the central tubular core (4) so that it is able to pass through the central tubular core (4) and allow the modular cylinder cutting blade section (10) to rotate freely around the steel tube whilst providing a tight fit. A second modular cylinder cutting blade section (12) is mounted onto the steel tube in succession to the first modular cylinder cutting blade section (10) so that it is adjacent to the first modular cylinder cutting blade section (10). The castellations (34) of the first modular cylinder cutting blade section (10) slot into and engage with the recesses (36) of the second modular cylinder cutting blade section (12) as shown in FIG. 1. Because the castellations (34) of the first modular cylinder cutting blade section (10) engage with the recesses (36) of the second cutting blade section (12), any rotationAL movement of the first modular cylinder cutting section (10) around the steel tube causes the second modular cylinder cutting blade section (12) to rotates and vice versa.

[0051] When the two modular cylinder cutting blade sections (10; 12) are mounted on the steel tube intermeshed, the cutting bars (2) of the two modular cutting blade sections (10; 12) are aligned to produce one extended cutting bar (2) which spirals for the length of the two sections (10; 12) through 72° as shown in FIG. 1.

[0052] The other four modular cylinder cutting blade sections (14; 16; 18; 20) are similarly mounted on the steel tube so that adjacent castellations (34) on one modular cylinder cutting blade section meshes within the recesses (36) of the adjacent modular cylinder cutting blade section as shown in FIG. 1. Rotation of any one of the modular cylinder cutting blade sections (10; 12; 14; 16; 18; 20) results in rotation of them all. The cutting blades (2) of adjacent sections are aligned as shown in FIG. 1.

[0053] The cylinder blade is rotated in the mower by the free castellations on the end modular cylinder cutting section (20) at one end (40) engaging with a rotational drive mechanism (not shown) on the mower and the empty recesses (36) at the other end (42) of the cylinder blade engaging with a second rotational drive mechanism. Rotation of the drive mechanisms in unison rotates the end modular cylinder blade cutting sections (10; 20) and hence all the other modular cylinder cutting blade sections (12; 14; 16; 18). 

1. A cylinder cutting blade for a lawn mower characterised in that it comprises at least two modular cylinder cutting blade sections which are rotationally connected together in succession in such a manner that rotation of one modular cylinder cutting blade section results in rotation of the other modular cylinder cutting blade section.
 2. A cylinder cutting blade as claimed in claim 1, wherein each modular cylinder cutting blade section is a short cylinder cutting blade.
 3. A cylinder cutting blade as claimed in claim 1, wherein it is constructed from at least two modular cylinder cutting blade sections, each modular cylinder cutting blade section having a longitudinal axis and a locking mechanism wherein the modular cylinder cutting blade sections are mounted in succession so that their axes are substantially co-axial and the locking mechanism of each modular cylinder cutting blade section interacts with the locking mechanism of adjacent modular cylinder cutting blade sections to rotationally lock that modular cylinder cutting blade section to the adjacent modular cylinder cutting blade sections so that rotation of one modular cylinder cutting blade section results in rotation of the adjacent modular cylinder cutting blade sections.
 4. A cylinder cutting blade as claimed in claim 1, wherein the cylinder cutting blade comprises: a longitudinal axis; a plurality of cutting bars which spiral around the longitudinal axis; a frame to hold the cutting bars in their respective positions characterised in that the cylinder cutting blade is constructed from at least two modular cylinder cutting blade sections, each modular cylinder cutting blade section comprising: a longitudinal axis; a plurality of cutting bars which spiral around the longitudinal axis; a frame to hold the cutting bars in their respective positions; and a locking mechanism; wherein the modular cylinder cutting blade sections are mounted in succession so that their axes are substantially co-axial and the locking mechanism of each modular cylinder cutting blade section interacts with the locking mechanism of adjacent modular cylinder cutting blade sections to rotatably lock the modular cylinder cutting blade section to the adjacent modular cylinder cutting blade sections so that rotation of the modular cylinder cutting blade section results in rotation of adjacent modular cylinder cutting blade sections.
 5. A cylinder cutting blade as claimed in claim 4, wherein the cutting bars of each modular cylinder cutting blade section spiral around the longitudinal axis of the modular cylinder cutting blade section from a first end to the other second end.
 6. A cylinder cutting blade as claimed in claim 5, wherein all the cutting bars in each modular cylinder cutting bar section spiral around the longitudinal axis of the modular cylinder cutting blade section in the same direction.
 7. A cylinder cutting blade as claimed in claim 5, wherein the cutting bars of each modular cylinder cutting blade section spiral around the longitudinal axis at a uniform rate.
 8. A cylinder cutting blade as claimed in 4, wherein the cutting bars of each modular section are capable of being aligned with the cutting bars of adjacent modular cylinder cutting blade sections.
 9. A cylinder cutting blade as claimed in any claim 1, wherein the locking mechanism of each modular cylinder cutting blade section comprises a first part mounted on one end of the modular cylinder cutting blade section and a second part mounted on the other end of the modular cylinder cutting blade section, the first part of the locking mechanism on one modular cylinder cutting blade section interacting with the second part of the locking mechanism on the adjacent modular cylinder cutting blade section.
 10. A cylinder cutting blade as claimed in claim 1, wherein all of the modular cylinder cutting blade sections are identical in shape.
 11. A cylinder cutting blade as claimed in claim 9, wherein the first part of the locking mechanisms on each modular cylinder cutting blade section comprise castellations.
 12. A cylinder cutting blade as claimed in claim 9, wherein the second part of the locking mechanisms on each modular cylinder cutting blade section comprise recesses.
 13. A cylinder cutting blade as claimed in claim 1, wherein the frame for each modular cylinder cutting blade section comprises a tube, which runs the length of the modular cylinder cutting blade section, the longitudinal axis of the tube being the longitudinal axis of the modular cylinder cutting blade section.
 14. A cylinder cutting blade as claimed in claim 13, wherein the frame comprises arms which project from the ends of the tube substantially perpendicular to the longitudinal axis of the tube, on the ends of which are rigidly mounted the cutting bars.
 15. A cylinder cutting blade as claimed in claim 13, wherein the modular cylinder cutting blade sections are mounted in succession on a rod or tube which passes through the tubes of the modular cylinder cutting blade sections.
 16. A cylinder cutting blade as claimed in claim 13, wherein the castellations of the locking mechanism of each modular cylinder cutting blade section are formed around the entrance of one end of the tube of that modular cylinder cutting blade section.
 17. A cylinder cutting blade as claimed in claim 13, wherein the recesses of the locking mechanism of each modular cylinder cutting blade section are formed around the other end of the tube of modular section.
 18. A cylinder cutting blade as claimed in claim 1, wherein each modular cylinder cutting blade section is manufactured from glass filled polyamide.
 19. A cylinder cutting blade as claimed in claim 1, wherein each modular cylinder cutting blade section is manufactured in a one piece construction.
 20. A cylinder cutting blade as claimed in claim 1, wherein the outer edge of each cutting bar of each modular cylinder cutting blade section is of constant radial distance from the longitudinal axis of that modular axis.
 21. A cylinder cutting blade as claimed in claim 1, wherein the length D of one or each of the modular cylinder cutting blade sections is equal to or less than $\frac{{\Pi \left( {S + {2t}} \right)} - {2{nc}}}{n\left( {{\tan \quad \theta_{1}} + {\tan \quad \theta_{2}}} \right)}$

where S is the internal diameter of a tube which runs the length of the modular cylinder cutting blade section; t is the thickness of the tube; n is the number of cutting bars; c is the tooling land; θ₂ is the shut off angle; and θ₁ is the helix angle at the outer diameter of the tube.
 22. A cylinder cutting blade as claimed in claim 1, wherein one or each of the modular cylinder cutting blade sections is moulded using a two piece mould.
 23. A lawn mower comprising a cylinder cutting blade as claimed in claim
 1. 24. A lawn mower as claimed in claim 23, wherein the cylinder cutting blade is rotatingly driven by a motor via at least one part of a locking mechanism of a modular cylinder cutting blade section located at the end of the row of successive modular cylinder cutting blade sections.
 25. A lawn mower as claimed in claim 23, wherein the cylinder cutting blade is rotatingly driven by a motor via at least one part of the locking mechanism of the modular cylinder cutting blade sections located at both ends of the row of successive modular cylinder cutting blade sections.
 26. A modular cylinder cutting blade section characterised in that it is capable of connecting to at least one other modular cylinder cutting blade section in succession to form a longitudinal cylinder cutting blade so that rotation of the modular cylinder cutting blade section results in rotation of the other modular cylinder cutting blade section.
 27. A modular cylinder cutting blade section as claimed in claim 26 for a cylinder cutting blade for a lawn mower comprising a longitudinal axis and a locking mechanism wherein the modular cylinder cutting blade section is capable of being mounted in succession with another modular cylinder cutting blade section so that their axes are substantially co-axial and the locking mechanism of the modular cylinder cutting blade section capable of interacting with the locking mechanism of an adjacent modular cylinder cutting blade section to rotationally lock the modular cylinder cutting blade section to an adjacent modular cylinder cutting blade sections so that rotation of the modular cylinder cutting blade section results in rotation of an adjacent modular cylinder cutting blade section.
 28. A modular cylinder cutting blade section as claimed in claim 26 comprising: a longitudinal axis; a plurality of cutting bars which spiral around the longitudinal axis; and a frame which locates the cutting bars in their respective positions, characterised in that it further comprises a locking mechanism which is capable of interacting with a locking mechanism of a second modular cylinder cutting blade section so that, when a second modular cylinder cutting blade section is mounted adjacent to the modular cylinder cutting blade section with its longitudinal axis substantially co-axial, the locking mechanism interacts with a locking mechanism of the second modular cylinder cutting blade section to rotatably lock the modular cylinder cutting blade section to a second modular cylinder cutting blade section so that rotation of the modular cylinder cutting blade section results in the rotation of a second modular cylinder cutting blade section.
 29. A modular cylinder cutting blade section as claimed in claim 26, wherein the cutting bars spiral around the longitudinal axis of the modular cylinder cutting blade section from a first end to the other second end.
 30. A modular cylinder cutting blade section as claimed in claim 29, wherein all the cutting bars spiral around the longitudinal axis of the modular cylinder cutting blade section in the same direction.
 31. A modular cylinder cutting blade section as claimed in claim 29, wherein the cutting bars of each modular cylinder cutting blade section spiral around the longitudinal axis at a uniform rate.
 32. A modular cylinder cutting blade section as claimed in claim 28, wherein the cutting bars are capable of being aligned with the cutting bars of an adjacent modular cylinder cutting blade section.
 33. A modular cylinder cutting blade section as claimed in claim 26, wherein the locking mechanism comprises a first part mounted on one end of the modular cylinder cutting blade section and a second part mounted on the other end of the modular cylinder cutting blade section, the first part of the locking mechanism on the modular cylinder cutting blade section is capable of interacting with a second part of a locking mechanism on an adjacent modular cylinder cutting blade section.
 34. A modular cylinder cutting blade section as claimed in claim 33, wherein the first part of the locking mechanisms comprises castellations.
 35. A modular cylinder cutting blade section as claimed in claim 33, wherein the second part of the locking mechanism comprises recesses.
 36. A modular cylinder cutting blade section as claimed in claim 26, wherein the frame comprises a tube, which runs the length of the modular cylinder cutting blade section, the longitudinal axis of the tube being the longitudinal axis of the modular cylinder cutting blade section.
 37. A modular cylinder cutting blade section as claimed in claim 36, wherein the frame comprises arms which project from the ends of the tube substantially perpendicular to the longitudinal axis of the tube, on the ends of which are rigidly mounted the cutting bars.
 38. A modular cylinder cutting blade section as claimed in claim 36, wherein the modular cylinder cutting blade section is mounted on a rod or tube which passes through the tube of the modular cylinder cutting blade section.
 39. A modular cylinder cutting blade section as claimed in claim 36, wherein the castellations of the locking mechanism are formed around the entrance of one end of the tube.
 40. A modular cylinder cutting blade section as claimed in claim 36, wherein the recesses of the locking mechanism are formed around the other end of the tube.
 41. A modular cylinder cutting blade section as claimed in claim 26, wherein it is manufactured from glass filled polyamide.
 42. A modular cylinder cutting blade section as claimed in claim 26, wherein each modular cylinder cutting blade section is manufactured in a one piece construction.
 43. A modular cylinder cutting blade section as claimed in claim 26, wherein the outer edge of each cutting bar is of constant radial distance from the longitudinal axis.
 44. A modular cylinder cutting blade section as claimed in claim 26, where its length D is equal or less than $\frac{{\Pi \left( {S + {2t}} \right)} - {2{nc}}}{n\left( {{\tan \quad \theta_{1}} + {\tan \quad \theta_{2}}} \right)}$

where S is the internal diameter of a tube which runs the length of the modular cylinder cutting blade section; t is the thickness of the tube; n is the number of cutting bars; c is the tooling land; θ₂ is the shut off angle; and θ₁ is the helix angle at the outer diameter of the tube.
 45. A modular cylinder cutting blade section as claimed in claim 26, wherein it is moulded using a two piece mould. 